This invention relates generally to the field of medical devices for delivering contrast media during medical diagnostic and therapeutic imaging procedures and more particularly, this invention relates to improved contrast media delivery systems and methods of use which allow adjustment of contrast media concentration and injection parameters either before or during an injection procedure to provide patient specific dosing of contrast media, thus decreasing the waste and cost of these procedures while increasing their efficiency.
It is well recognized that the appropriate dose for many medications is related to the size and weight of the patient being treated. This is readily apparent in the difference between the recommended doses which most medications have for adults and children. The appropriate dose of contrast media for a given medical imaging procedure is equally dependent upon the size and weight of the patient being examined as well as other additional factors.
Although differences in dosing requirements for medical imaging procedures have been recognized, conventional medical imaging procedures continue to use pre-set doses or standard delivery protocols for injecting contrast media during medical imaging procedures. Using fixed protocols for delivery simplifies the procedure, however, providing the same amount of contrast media to patients weighing between 100 and 200 pounds, for example, produces very different results in image contrast and quality. If the amount of contrast media used is adequate to obtain satisfactory imaging for the 200 pound person, then it is likely that the 100 pound person will receive more contrast media than necessary for the procedure to produce a diagnostic image. With high contrast costs, this is a waste of money as well as increased patient risk.
Standard protocols are used primarily to minimize the potential for errors by hospital personnel and decrease the likelihood of having to repeat the procedure, an occurrence which requires that the patient be exposed to additional radiation and contrast media. Furthermore, in prior art contrast delivery systems, once a bottle of contrast media was opened for use on a patient it could not be used on another patient due to contamination considerations. Existing contrast delivery systems do not prevent the source of contrast media used for an injection from being contaminated with body fluids of the patient. The containers which supplied the contrast media were generally therefore all single use containers and, consequently, the entire container of contrast media was given to the patient being studied.
Present protocols include delivery rate in volume per unit time. Usually the injection is at a constant flow rate or with one change between two fixed flow rates. However, physically, pressure drives fluid flow. Thus, present fluid delivery systems employ some type of servo to develop the pressure needed to deliver the programmed flow rate, up to some pressure limit. The pressure needed depends upon the viscosity of the fluid, the resistance of the fluid path, and the flow rate desired. This is considerably better than the older injector systems which controlled pressure at a set value, and let the flow rate vary.
There are significant drawbacks to fluid delivery systems which are unable to adjust the concentration of contrast media and other injection parameters during an injection procedure. Many patients may receive more contrast media than is necessary to produce an image of diagnostic quality, while others may receive an amount of contrast media insufficient for producing a satisfactory image. Existing procedures also frequently result in waste of contrast media as well as the need for repeating the procedure because an image of diagnostic quality could not be produced.
Some of the shortcomings of existing procedures have been addressed and resolved as described in co-pending application Ser. No. 08/144,162, titled xe2x80x9cTotal System for Contrast Delivery,xe2x80x9d filed Oct. 28, 1993, and incorporated herein by reference. This application discloses a contrast media delivery system which provides a source of contrast media that is sufficiently isolated from a patient undergoing an imaging procedure that the source of contrast media may be used on additional patients without concern for contamination. Additionally, this system is capable of adjusting contrast media concentration and other injection parameters during an injection procedure.
The system incorporates a source of contrast media and, if desired, a diluent. Each is sufficiently isolated from the patient to prevent contamination. The contrast media preferably has a concentration which is the highest that would be used in an injection procedure so that the operator may combine the contrast media with a diluent and select virtually any concentration of contrast media desired for any given procedure. The concentration of the contrast media injected into a patient may be varied during the injection procedure by varying the ratio of diluent to contrast media. Each patient therefore receives only the amount of contrast media necessary to provide a proper diagnostic image.
It is recognized that this system will be much more versatile and useful if the operator is able to select and adjust contrast media concentration and other injection parameters based on patient information or feedback received during the injection imaging procedures. Additionally, this system would be more efficient if it were capable of automatically choosing the appropriate concentration and injection rate for a given patient. Even more utility and efficiency would be realized from a system that is capable of automatically adjusting concentration and other injection parameters during an injection procedure based on feedback related to the resultant image quality.
Accordingly, it is an object of this invention to provide an improved contrast media delivery system which is capable of automatically varying the injection rate and concentration of contrast media given to a patient during an imaging procedure, based on information received either before or during the injection procedure.
It is another object of the present invention to provide an improved contrast media delivery system which obtains and utilizes feedback information during the imaging procedure to automatically adjust the flow rate, volume and/or concentration of the contrast media into the patient if needed.
It is a further object of this invention to provide a system which is capable of selecting the appropriate injection flow rate and concentration for a given patient based on patient information entered into the system.
Numerous other objects and advantages of the present invention will become apparent from the following summary, drawings, and detailed description of the invention and its preferred embodiment.
The invention includes apparatus and methods for medical contrast imaging and comprises embodiments which provide patient specific dosing of contrast media in a variety of medical imaging procedures, as opposed to fixed protocols. In this invention, the protocol variables are determined by the system and are dependent upon patient specific information supplied by the operator, and/or information measured by the contrast delivery system either prior to, or during the injection procedure. These apparatus and procedures disclosed herein apply to all of the systems disclosed and described in co-pending application titled xe2x80x9cTotal System for Contrast Deliveryxe2x80x9d, Ser. No. 08/144,462. Further systems are described in which the system receives input from an operator to provide the appropriate adjustment of system parameters.
In a principal embodiment, information specific to any given patient is entered into the system and the appropriate concentration and injection parameters are computed before initiating the imaging fluid injection procedure. The system is then ready for injection of a patient. It is important to note that the system is not limited to choosing a particular concentration of contrast media or injection rate for the entire procedure, or even a moderate number of phases with constant velocity as present injectors can now do, but rather is capable of selecting an injection profile which may include a continuously varying injection rate and/or concentration of contrast media. The particular injection profile selected by the system is designed to provide the best image quality for the particular patient based on a variety of factors such as patient weight and circulation system variables.
In a refined version of the system, feedback from at least one sensor is employed by the control system to modify the concentration of the contrast media, injection rate, and/or total volume during the injection procedure. Various types of sensors are disclosed for use with this system, in particular, various electromagnetic sensors or video monitoring devices provide feedback for the system or operator to use. In angiography, where the contrast is injected into the region of interest, the sensor needs to make a measurement in that region of interest. In CT and MR it is sufficient for the sensor to measure a remote area of the body, although measuring within the region of interest (ROI) could be advantageous in some applications. The sensor provides an indication of the actual amount of contrast media in the patient. This is used to calculate the appropriate injection rate or concentration of contrast media to provide a diagnostic image with minimum risk and cost.
In critical locations such as coronary arteries, it will take a while for doctors to have confidence in automatically controlled fluid delivery system, thus, rather than automatically altering injection parameters based on feedback signals received from automatic sensors, the concentration, or other injection parameters may be manually adjusted based on images seen by the doctor or operator.
A final version of the invention is disclosed which works to further improve doctors confidence by providing tactile feedback to a doctor or operator in addition to visual or other sensed feedback on the amount of contrast media in a patient. This provides the operator with additional information to use in determining injection rate, concentration and pressure for the injection procedure.